The long-term goal of the proposed research is the increased understanding of the neural control of eye movement. The major aim during the requested grant period will be the clarification of the role of the cerebral cortex in oculomotor control, with particular emphasis on the contribution of posterior parietal association cortex. This region is of speical interest because several lines of evidence indicate that the inferior parietal lobule (area 7 of Brodmann) may be involved in the initiation and control of eye movements concerned with the maintenance of gaze upon a visual target of motivational interest. Area 7 sends anatomical projections to other regions of the nervous systems which are known to be concerned with eye movement; electrical stimulation of area 7 causes conjugate eye movements; and oculomotor disorders are commonly associated with posterior parietal damage in the clinical literature. Furthermore, neurons have recently been discovered in area 7 which discharge a high frequency burst of action potentials as much as 150 msec before target-directed saccadic eye movements in monkeys. Other neurons maintain a high rate of activity while a monkey visually fixates an object of motivational interest, and this neural activity is suppressed 50-100 msec prior to a saccadic eye movement to a new target. Another class of cells is tonically active during the visual tracking of a slowly moving target, but not during fixation of a stationary target, or before saccades. The proposed research will determine whether axons from these saccade, fixation, and tracking cells of area 7 project to the brainstem oculomotor system or the frontal eye fields. The methods of single-unit analysis in behaving monkeys and of antidromic activation of the axons of area 7 cells by stimulating electrodes placed in likely anatomical projection target regions will be used. A second goal for the proposed grant period is to determine quantitatively the exact oculomotor deficits which follow surgical ablation of area 7 in behaviorally trained monkeys.